The present invention relates generally to valve apparatus used in a string of tubing or drill pipe disposed in a well bore, and particularly to a new and improved type of tubing tester valve which may be incorporated in a string of tubing or drill pipe being run into a well bore and employed to pressure test the integrity of the string.
Numerous well service operations entail running a packer into a well bore at the end of a string of tubing or drill pipe, and setting the packer to isolate a producing formation or "zone" intersected by the well bore from the well bore annulus above the packer. After this isolation procedure, a substance such as a cement slurry, an acid or other fluid is pumped through the tubing or drill pipe under pressure and into the formation behind the well bore casing through perforations therethrough in an area below the packer. One major factor in ensuring the success of such an operation is to have a pressure-tight string of tubing or drill pipe.
Another common well service operation in which it is desirable to assure the pressure integrity of the string of tubing or drill pipe is the so-called drill stem test. Briefly, in such a test, a testing string is lowered into the well to test the production capabilities of the hydrocarbon producing underground formations or zones intersected by the well bore. The testing is accomplished by lowering a string of pipe, generally drill pipe, into the well with a packer attached to the string at its lower end. Once the test string is lowered to the desired final position, the packer is set to seal off the annulus between the test string and the well casing, and the underground formation is allowed to produce oil or gas through the test string. As with the previously mentioned well service operations, it is desirable prior to conducting a drill stem test, to be able to pressure test the string of drill pipe periodically so as to determine whether there is any leakage at the joints between successive stands of pipe.
To accomplish this drill pipe pressure testing, the pipe string is filled with a fluid and the lowering the pipe is periodically stopped. When the lowering of the pipe is stopped, the fluid in the string of drill pipe is pressurized to determine whether there are any leaks in the drill pipe above a point near the packer at the end of the string.
In the past, a number of devices have been used to test the pressure integrity of the pipe string. In some instances, a closed formation tester valve included in the string is used as the valve against which pressure thereabove in the testing string is applied. In other instances, a so-called tubing tester valve is employed in the string near the packer, and pressure is applied against the valve element in the tubing tester valve.
As it is necessary to fill the tubing or drill pipe string with an incompressible fluid as the string is run into the well bore before applying pressure to the interior of the string. Some prior art tubing tester valves, when used in a string without a closed formation tester valve therebelow, rely upon the upward biasing of a flapper valve element against a spring by hydrostatic pressure below the tubing tester valve in the test string to gradually fill the test string from below with fluid in the well bore, generally drilling "mud." In other instances, the test string is filled from the top on the rig floor with diesel oil or other fluids, such a procedure being easily appreciated as time consuming and hazardous. Still other prior art tubing tester valves incorporate a closeable bypass port below the valve element so that, even with a closed formation tester valve below, well fluids in the annulus surrounding the test string can enter in the vicinity of the tubing tester valve and bias a valve element therein to an open position through hydrostatic pressure, thereby filling the string.
At some point during the well service operation, be it cementing, treating or testing, it is necessary to be able to open the tubing tester valve so that flow from the rig floor down into the formation, which would normally close the valve, may be effected. Prior art tubing tester valves accommodate this necessity in several ways. Some valves provide for the opening of the tubing tester valve through reciprocation and/or rotation of the pipe string, while other prior art valves provide for the opening of the valve through a valve actuator operated responsive to an increase in annulus pressure.
The form that the valve element in prior art tubing tester valves may take has also been varied. Ball valves, flapper valves, and even sleeve valves, where it is not necessary or desirable to have a fully open bore from the top of the pipe string to the bottom, have been employed.
All of the prior art tubing tester valves, however, have suffered from various deficiencies relating to the complexity of their operating mechanisms, or from a necessity to reciprocate or otherwise move the pipe string in order to open a valve element therein against flow from the surface to a formation below the packer.